1. Field of the Invention
The present invention relates to interpreting non-invasive scans of a knee of a subject to determine properties of a meniscus of the knee, and, in particular, to determining one or more properties of the meniscus, such as tears, without human intervention.
2. Description of the Related Art
The meniscus is an important part of the knee support mechanism. It includes 2 large C-shaped (medial side) and O-shaped (lateral side) structures and acts as a cushion between the femur and the tibia. Although the meniscus is highly tolerant to axial forces, it is susceptible to rotational forces, which may result in meniscal tearing. If a tear originating in the periphery of the meniscus is left untreated, it propagates easily and may affect the mechanical integrity of the entire knee joint. Knee-related injuries, including meniscal tears, are common in both young athletes and the aging population, requiring accurate diagnosis and, when appropriate, surgical intervention. Despite the frequency of such injuries, few published studies have focused on means to enhance and refine detection of meniscal tears. (See for example, Y Hata, S Kobashi, S Tokimoto, M Ishikawa, H Ishikawa, “Computer-aided diagnosis system of meniscal tears with T1- and T2-weighted MR images based on fuzzy inference,” Lect Notes Comput Sci, vol. 2206, pp 55-58, 2001).
The meniscus is a soft tissue feature with low contrast in imagery from many scanning devices, such as X-rays and X-ray computer tomography (CT) scans. The superior soft-tissue contrast and spatial resolution provided by magnetic resonance (MR) imaging enables radiologists to characterize and differentiate pathologic from normal soft tissue, including meniscus tissue. MR imaging offers significant and specific help in the diagnosis of internal derangements of the knee, including meniscal tears. A normal meniscus appears as uniform, low-signal triangles or polygons on certain slices of MR imaging. However, when the meniscus is torn, the normal low-signal appearance is disrupted. A meniscal tear, then, can be detected if the normal shape of the meniscus is disrupted by an abnormal signal or if part of the meniscus is missing. Challenges in diagnoses of meniscal pathology include differentiation of tears, which indicate a need for surgery, from internal degenerative change, which would obviate the need for surgery.
With proper techniques and experienced skills, confidence in detection of meniscal tears by a skilled radiologist can be quite high. However, for radiologists without musculoskeletal training, diagnosis of meniscal tears can be challenging. Even for highly experienced radiologists, the effort to explore multiple images from the MR scans and identify views of the meniscus with sufficient area and detail to detect tears is tedious and time consuming and can lead to errors of omission if a salient scan slice is skipped.